1. Field of the Invention
The subject invention is directed to inertial measurement systems, and more particularly, to an inertial measurement unit that blends the output from an arrangement of low-bandwidth gyroscopes with the output from an arrangement of high-bandwidth accelerometers to extend the effective bandwidth of the system.
2. Description of Related Art
Micro-electric mechanical sensors (MEMS) are often used as gyroscopes (gyros) and accelerometers to perform inertial measurements in inertial navigation systems employed in vehicles. For example, a standard inertial measurement unit (IMU) uses a triad or three-axis gyro arrangement to sense angular rate (sometimes referred to as angular velocity). Accelerometers are used to sense linear acceleration along a given axis and are also used to sense tangential acceleration due to changing angular rate (sometimes referred to as angular acceleration). Prior art IMUs have employed accelerometers as a redundant source of angular rate in the event of a gyro sensor failure, and accelerometers have also been employed in gyro-less IMUs.
Current MEMS gyros are limited in effective bandwidth because of the high noise levels that are inherently associated with them, such as, for example, gyro angle random walk noise and gyro rate random walk noise. Furthermore, high bandwidth MEMS gyros are relatively expensive as compared to MEMS accelerometers of much higher bandwidth. In general, the bandwidth of the accelerometers used in an IMU is an order of magnitude higher than the bandwidth of the gyros used in an IMU. It would be beneficial to extend the effective bandwidth of a gyro-based IMUs angular rate output by taking advantage of less expensive, higher bandwidth accelerometers.